1. Field of the Invention
The present invention relates to a method of removing any residual photoresist that remains after photoresist development. More particularly, the present invention relates to a method of removing residual color photoresist from a developed color photoresist layer often used as an image sensor.
2. Description of the Related Art
A digital color image is normally formed by shining a beam of light through a stack of color filter arrays (CFA) so that the image is intercepted by a charge coupled device (CCD) or a CMOS image sensor. In general, a CFA consists of three or more color filtering channels alternately positioned such that each color filter channel permits only a designated frequency bandwidth in the visible light spectrum to pass to an image sensor. Hence, color content of a photographic image is determined by various elements in the CFA. Typical color elements used in a CFA includes red, green, blue (RGB) or cyan, magenta, yellow (CMY) or some other assembly of colors.
FIG. 1 is a schematic cross-sectional view showing a RGB color photoresist layer 12 formed over a CMOS transistor substrate 10 in the process of forming the image sensor of a CFA. In general, the photoresist layer is formed on a rough substrate surface. Since the photoresist layer is neither smooth nor uniform in thickness, diffused light is often produced in the process of transferring a pattern to the photoresist layer, resulting in some residual photoresist material 14 in the supposedly blank region 20. Another source that may contribute to the appearance of photoresist material 14 inside the blank region 20 is an improper setting of baking temperature or duration. The resulting residual photoresist material is very difficult to remove by conventional cleaning processes. However, if the residual photoresist is not removed from the blank area 20, product quality is likely to be affected.
Accordingly, one object of the present invention is to provide a method capable of removing residual color photoresist without affecting the color photoresist pattern.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of removing any residual color photoresist that remains on a substrate after a patterned color photoresist layer is formed over the substrate. The method includes aiming a high-pressure jet of de-ionized water that contains an interface-activating agent at the substrate.
The invention also provides a second method of removing any residual color photoresist that remains on a substrate after a patterned color photoresist layer is formed over the substrate. The method includes aiming oxygen plasma at the substrate so that the residual photoresist material is polarized. The polarized residual photoresist material is next removed by de-ionized water.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.